What is the meaning of vector<vector<ll>> a(k,vector<ll>)

#1

I’ve just seen the video on the implementation of matrix exponentiation.

What is the meaning of the term “vector<‘vector’> A(k,vector<‘ll’>)” ?

#2

vector < vector< ll >> a means that it is similar to a 2d array

#3

But, what is the meaning of A(k , vector)

#4

k is the number of rows in the 2d vector and vector is used as a parameter to show that it is a vector of vectors